Improvement of Intake Restrictor Performance for a Formula SAE Race Car through 1D & Coupled 1D/3D Analysis Methods

A typical means of limiting the peak power output of race car engines is to restrict the maximum mass flow of air to the engine. The Formula SAE sanctioning body requires the use of an intake restrictor to limit performance, keep costs low, and maintain a safe racing experience. The intake restrictor poses a challenge to improving engine performance. Methods to better understand the ramifications of the restrictor on the engine lead to performance improvements that allow an edge over the competition.

A one-dimensional gas exchange simulation code coupled with three-dimensional CFD is used to simulate various concepts in the improvement of restrictor performance. Ricardo's WAVE and VECTIS are the respective simulation codes. Along with this, the interaction of intake manifold and restrictor are considered. The effects of different diffuser geometries and plenum dimensions were first explored using WAVE, and then a series of different diffuser angles were simulated using WAVE-VECTIS. Primary area of improvement was determined to be through the use of tighter or smaller diffuser angles.

Acoustic filtering using Helmholtz resonators was investigated using WAVE to determine if restrictor performance could be improved by attempting to make flow at the throat more uniform over the cycle. Inline Helmholtz resonators were also investigated in an attempt to increase pressure upstream of the throat. Initial results were encouraging, but were very sensitive to geometry. An additional coupled simulation considered the effect of swirl vanes placed upstream of the restrictor throat. Swirl vanes had little to no effect on the performance of the intake.